Within the past several years the development of ferrous wire reinforced rubber based products such as tires, hose and conveyor belts has become prominent. With these developments, the aged adhesion between the metallic wire and the vulcanized rubber based material has become of critical importance.
Previous attempts to improve the adhesion between the metallic wire and the rubber based material have included coating the metallic wire with brass, a binary alloy composed of copper and zinc. Although brass coated metallic wire is probably the most widely used material in the rubber tire industry, surface phenomenon occuring between the brass coated wire and the rubber based material have prevented brass coated wire from having wide spread application within the tire industry and from having wide spread application with respect to various rubber based compositions and materials. For example, it is believed that moisture and oxidation phenomenon on the surface of the brass coated metallic wire cause adverse effects upon the aged adhesion of rubber to the metallic surface.
Accordingly, various attempts have been suggested to improve the adhesion between the rubber based material and the metallic surface such as the utilization of organic adhesive materials on the brass surface, the utilization of thin films of metals on the surface of the brass, and the utilization of thin films of metals between the metallic wire and the brass outer surface to somehow increase and aid in the adhesion between the metallic wire and the rubber based material.
Although such suggestions and attempts may under certain conditions provide adequate adhesion between the metal substrate material and a specific rubber based composition, commercial application of such suggestions have not been utilized. For example, the composition of the rubber based materials, such as rubber tire compositions, are largely proprietary to the major rubber companies and the specific identification of the composition thereof vary from manufacturer to manufacturer. Thus, a particular treated metal substrate may adhere well with a particular manufacturer's rubber based composition and the same material will not adhere well to a second manufacturer's rubber based composition. Additionally, the placing of a thin film of any number of specific metals on the outside surface of the brass coated steel wire or between the steel and the brass coating has substantially reduced the ability of such treated wires to be drawn to the precise specifications necessary for insertion into tire materials, thus resulting in a metallic substrate material which is commercially undesirable and unacceptable.